It is conventional practice in the construction of chairs, particularly for commercial and office use to provide means whereby the chair may be rotated, that is swiveled, and also the height of the seat can be vertically adjusted. In some cases, rotation is accomplished by means of casters on the base and, in other cases, the chair is made rotatable by the construction of its supporting spindle or standard. Vertical adjustment of the seat height is normally accomplished by providing a threaded member which, upon rotation of the seat, raises or lowers the height of the seat.
The problem of providing both in a simple structure non-height adjusting rotation and height adjustment has not heretofore been satisfactorily solved. The problem arises from the fact that if the seat is made freely rotatable on the spindle, it has then not been possible to make the vertical adjustment by means of a threaded member without the use of complicated locking and release mechanisms. These mechanisms have required the operator to manipulate various handles or loosen various screws or nuts so that rotation of the seat will either effect vertical adjustment or it will be functionally disconnected from the threaded member so that the threaded member remains stationary even though the seat is rotated. This arrangement has proved particularly unsatisfactory not only from a functional but also from an aesthetic point of view.